Filters for cleaning liquid or gaseous media in motor vehicles are used in a very wide variety of embodiments, for example as oil filters for operating a combustion engine. In order to ensure consistent lubrication of the combustion engine, burnt oil fractions, metal abrasion and other contaminants are filtered out by means of a suitable oil filter. For this purpose, the oil filter is located in an oil supply circuit connected to the combustion engine.
In this context, the publication DE 100 46 494 A1 discloses a filter assembly for filtering in particular oil for lubricating an internal combustion engine of a motor vehicle. The filter assembly consists of a filter housing, a filter cover and a filter insert arranged in the filter housing. The filter cover can be connected in a liquid-tight manner to the filter housing by means of a screw connection, wherein the filter insert can be interchanged if the need arises by unscrewing of the filter cover.
The filter insert, which is generally designed as a disposable article, has, as the element active in the filtering, an open-pored paper membrane which is folded in a zigzag-shaped manner and through which the oil to be filtered passes during the operation of the motor vehicle. Since the surface of the paper membrane becomes clogged with contaminants over the course of time, regular replacement of the filter insert is needed during maintenance work in order to avoid the throughflow or filter capacity being impaired. In this case, the used filter insert is disposed of and replaced by a new one.
If, during such maintenance work, the filter insert is removed from the filter housing but the fitting of a new filter insert is forgotten and, as a consequence, the filter assembly is operated with the filter insert missing, there is the possibility of contaminated oil being able to pass unnoticed into the motor vehicle units connected to the filter assembly.